Central heating pump failure and replacement
A boiler that gets hot while radiators stay cold usually points at circulation, not combustion. Pumps seize after long summer standstills, and older fixed-speed models draw far more electricity than a modern modulating replacement.
Diagnosis, then choice of replacement
We check for power at the pump, listen for a running but non-circulating rotor, and test flow across it. Seized rotors sometimes free with a manual turn, which confirms the diagnosis but rarely lasts. When replacing we fit a modulating pump wherever the system suits one, which cuts running cost and reduces velocity noise.
Replacement job scope
- Isolate, drain locally and swap without a full system drain where possible
- Correct head and flow rating for the property, not the old model number
- Speed set against measured flow and return differential
- System re-inhibited and air purged properly on refill
Frequently asked
- Can a stuck pump be freed?
- Sometimes, with the central screw. Treat it as a temporary measure — a pump that's seized once usually does it again.
- Are modern pumps quieter?
- Noticeably. Modulating pumps drop speed when zones close, which removes most of the whoosh and vibration people notice at night.
- Is the pump inside my combi?
- Yes on combis and most system boilers, so replacement is an internal part rather than a separate pump on the pipework.
Quick job when diagnosed properly
Most pump replacements are done in a single visit. We'll confirm circulation with measured temperatures before we leave rather than just listening for a hum.
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